1. Field of the Invention
The present invention relates to an electronic device that includes a printed circuit board and an electronic element mounted on the printed circuit board.
2. Description of the Related Art
According to the prior art, an electronic device that includes a printed circuit board and an electronic element mounted on the printed circuit board has an insertion mounting structure and a surface mounting structure.
For example, in an electronic device disclosed in JP-A-11-317265, end portions of leads (i.e., branch terminals) of an electronic element (i.e., a connector) are formed by punching to have inverted L-shapes. Each of the branch terminals has a horizontal portion (i.e., surface section) and a vertical portion (i.e., insertion section) that are integrally formed. The surface section is joined to a surface of a lead-connecting land (i.e., surface land). The insertion-section is inserted into a through hole provided at a printed wiring board.
When the insertion section is inserted into the through hole in which a solder paste is applied, air may be caught in the solder paste. In addition, a flux and a solvent component in the solder paste are gasified in the solder paste at a reflow process. The bubbles of air and gas move in the melted solder paste (i.e., in the through hole) toward an upper surface of the printed circuit board on which the electronic element is disposed.
When the electronic element has the branch terminals, the surface sections of the branch terminals are located on the upper-surface side of the printed circuit board, which is the same side as the bubbles move to. The surface sections are located over at least portions of the through holes and the surface lands. In addition, in a thickness direction of the printed circuit board, lower surfaces of the surface sections are same height as upper surfaces of the surface lands or the lower surfaces of the surface sections are slightly away from the upper surfaces of the surface lands. Thus, even if the bubbles move upward and contact the surface sections, and then move in a direction perpendicular to the through holes (i.e., horizontal direction), sidewalls of the through holes are located in the moving direction. Thereby, the surface sections of the branch terminals restrict the movement of the bubbles. If a part of the bubbles remains in the solder paste, a void may be generated when the solder pasted is cooled and solidified. As a result, the branch terminals are difficult to be coupled with the printed circuit board with a high degree of certainty.